The present invention relates to an electronic regulation module for the movement of a mechanically wound watch, and a process for regulating the speed of a mechanically wound watch movement by means of an electronic module.
All watches need a source of energy to drive the movement and move the hands.
In the case of mechanical watches, this energy is supplied by the user by winding the stem or, in the case of automatic watches, by movements of an oscillating mass arising from movement of the wrist and permitting loading a spring.
Mechanical watch movements most often use an anchor escapement as a regulation member to guarantee precise operation of the watch. This purely mechanical element however does not permit ensuring satisfactory precision of operation.
Electronic watches, particularly quartz watches, have greater precision. The energy is most often supplied by a battery. These batteries have particularly the following drawbacks:
Requiring returning periodically to a watchmaker to replace the battery.
The risk of losing watertightness of the watch during that replacement.
Requiring distributing to a network of dealers a very large assortment of different batteries for as long a period as possible.
Ecological problems associated with disposal of the batteries.
Substantial cost of replacement and changing.
Different attempts have thus been carried out to omit batteries from quartz watches. The use of photovoltaic cells is attractive, but imposes substantial aesthetic drawbacks. Sources of energy based on temperature gradient or on the acidity of the skin of the wearer are also in an experimental stage. Other sources of energy envisageable for other portable apparatus cannot be sufficiently miniaturized to be integrated into the reduced volume of a wristwatch.
To prolong the lifetime of batteries, quartz watches are known in which the battery is recharged by a mechanical energy source. In this case, the mechanical energy produced by movements of the user is accumulated in a spring, as in automatic watches, then transmitted through a gear train to a generator which converts it into electrical energy used to recharge the battery. This battery supplies a conventional quartz movement with a stepwise clock motor. This system thus permits prolonging the lifetime of the battery, but not completely eliminating it. It is nevertheless quite necessary to replace it periodically. Moreover, these watches require a generator in addition to the motor, which gives rise to increased cost and occupies a substantial volume in the watch. Finally, the movement of the hands is characteristically jerky, which is not attractive, in watches with a stepwise motor.
The patent CH597636 provides a construction permitting completely eliminating the battery from a quartz watch. In this movement, the energy produced by movements of the user is accumulated in a spring, then transmitted through a gear train to the hands of the watch as well as to a generator which converts it into electricity (source of AC voltage). This voltage source is rectified so as continuously to supply an electronic circuit including a quartz oscillator. The electronic circuit adjusts the operation of the watch by acting on the electrical torque applied to the generator. When the generator turns too rapidly, the electronic circuit brakes it by short-circuiting it (all-or-nothing braking). The ideal reference speed is supplied by the quartz oscillator.
The document EP0 239 820 discloses a process for adjusting the speed of a generator in which the speed of the generator is also adjusted all-or-nothing, with the help of a brake control signal. The brake control signal is synchronized with a reference signal obtained from a quartz oscillator. At each cycle of the reference signal, the brake control signal passes first of all from the zero logic condition to the logic condition one, and then returns from the logic condition one to the zero logic condition.
The brake control signal thus depends solely on the reference signal and is not synchronized with the measuring signal produced by the generator. When the phase or frequency of the reference signal and of the measuring signal from the generator are quite different, which can take place for example at the startup of the system or following a violent shock, the control impulses of the brake can arise at the most unfavorable time for the generator, for example when the voltage at the output terminals just passes through a maximum. As will be seen later, this situation can give rise to abrupt stopping of the watch.
EP0 679 968 discloses another control module permitting applying xe2x80x9call-or-nothingxe2x80x9d braking to the generator. When the generator rotor advances, the control module sends very short control pulses which have the effect of short-circuiting the generator. Braking by short-circuiting being very abrupt, the duration of the braking pulses is necessarily very short.
The all-or-nothing braking process described in the above documents has the drawback of imposing very brief and very intense decelerations on the rotor of the generator. After each braking pulse, the rotor and the gear train need considerable energy to accelerate and then to return to a speed near the reference speed fixed by the quartz oscillator. This mode of operation by shock is thus less energetically efficient, such that sufficient autonomy of the watch can be obtained only by using energy storage means, in the mechanical form of a spring or in the electrical form of capacitors, which are very voluminous. The watch movements obtained with this technology thus cannot be miniaturized without decreasing the autonomy of the watch below an acceptable minimum.
The application EP0 816 955, to which the reader can profitably refer, as well as the patent EP0 848 842 disclose another control module permitting applying to the rotor of the generator a braking couple which depends on the advance of the rotor. The braking circuit comprises several impedances of different values, which can be independently selected to apply different separate braking couples that are not zero, to the generator. The resulting impedance of the braking circuit depends on the advance of said generator. This device thus permits applying a braking couple proportional to the advance of the generator. The generator is so dimensioned as to turn slightly more rapidly than the reference speed, so as to permit adjustment of the speed. In a stable state, the braking circuit thus brakes continuously with a braking couple much weaker than in the all-or-nothing braking systems. Braking is interrupted solely when the generator turns too slowly, for example at startup or following a shock. This module thus permits avoiding abrupt decelerations of the rotor and thus is more energy efficient.
The control module described in this document has however the drawback of braking even when the AC voltage at the terminals of the generator passes through a maximum. When the generator is advancing, which is to say in the most usual situation, the peak-to-peak voltage at the output terminals of the generator is thus reduced by this braking. The storage capacities hence can use only a decreased recharge voltage. So as to maintain sufficient supply voltage for the electronic circuit, it is thus necessary slightly to overdimension the generator or in any case to provide storage capacities of a sufficient value, for the energy.
This problem is even more crucial in the circuit disclosed by EP0 239 820 mentioned above, because in this case the braking pulses, which are synchronized with the quartz reference signal, can according to the relative dephasing of the measuring signal and of the reference signal sometimes be produced just at the time at which the voltage of the terminals of the generator is at a maximum. The short-circuiting of the generator produces an instantaneous abrupt voltage drop, such that the storage capacitances are not at all recharged. If the voltage in the storage capacitances falls below the minimum requirement, the circuit is in danger of completely stopping.
EP1 041 464 discloses a control module in which the brake is actuated by means of braking impulse trains. At each impulse, the rotor is abruptly braked, for a very short time, but nevertheless requiring an acceleration between two pulses. The rotor thus undergoes a multitude of successive accelerations and decelerations during each cycle. Moreover, the circuit does not permit preventing a braking pulse from taking place at the moment at which the voltage at the outlet of the generator passes through an extreme. Finally, the generator of these pulse trains require complex combination logic and consumes substantial current.
An object of the invention is to provide a new construction of a module for regulating a quartz watch without a battery, permitting overcoming the drawbacks of known constructions, particularly the problems of autonomy, volume and electrical storage in an electrochemical battery.
Another object of the invention is to provide a new construction of a regulation module for a quartz watch without a battery, permitting recovering with minimum loss the peak-to-peak voltage produced by the generator to supply the circuit whilst avoiding the problems of abrupt deceleration of the rotor arising in all-or-nothing braking modules by short-circuiting the generator.
Another object is to improve the braking process at several levels suggested by EP0 816 955 and to solve particularly the problem of peak-to-peak voltage drop arising from continuous braking.
Another object of the invention is to provide a new construction of a quartz regulation module without a battery, that can be produced and sold freely and independently of technologies proposed by other manufacturers.
These objects are achieved by means of a module having the elements disclosed below and by a process having the steps disclosed below.
In particular, these objects are achieved with the help of an electronic module for regulation of a watch movement with mechanical winding, comprising a generator permitting converting mechanical energy supplied by the mechanical watch movement into a measuring signal, an electronic circuit supplied by said generator and comprising a braking circuit permitting applying at least two separate braking couples that are not zero, to said generator, said electronic circuit moreover comprising a control circuit for the braking circuit, so as to control the speed of rotation of said generator, the braking couple selected by said control circuit depending particularly on the advance of the generator, and in which the braking couple is reduced when said measuring signal passes through an extreme.
Relative to the modules of the prior art, this regulation module has the particular advantage of reducing the braking when the measuring signal passes through an extreme. It is thus possible to use the peak-to-peak voltage of the measuring signal to charge the storage capacitors with sufficient energy to supply the circuit. As the braking circuit permits applying at least two separate braking couples that are zero, it is possible to reduce the braking without completely interrupting it, and thereby to avoid the abrupt decelerations typical of the all-or-nothing braking systems.
In a preferred modification, the braking is reduced during a fixed time, or at least a limited time, when the measuring signal passes through an extreme. The duration of reduction of braking is selected so as to be sufficient to guarantee a complete recharging of the storage capacitors, whilst leaving a sufficiently long braking time to permit precise regulation even with low braking couples.
In a preferred modification, the braking couple is progressively reduced before the, measuring signal passes through an extreme, then progressively re-established after said measuring signal has passed through said extreme. There is thus avoided all the shocks arising from abrupt variations of the applied braking couple.
Relative to modules known to the prior art, the module of the invention thus permits applying at each instant a braking couple which depends both on the advance of the rotor and on the instantaneous phase of the measuring signal at the terminals of the generator, so as to obtain the following advantages:
Avoiding abrupt braking pulses, most particularly when the measuring signal at the terminals of the generator passes through an extreme.
Avoiding abrupt variations in the braking couple, so as to maintain a speed of rotation of the rotor as constant as possible and as close as possible to the reference speed given by the quartz oscillator.
Recharging the storage capacitors at the time at which the output voltage of the generator passes through an extreme by reducing the braking, but without interrupting it abruptly.